A degree theorem for the simplicial closure of Auter space

The degree of a based graph is the number of essential nonbasepoint vertices after generic perturbation. Hatcher–Vogtmann’s degree theorem states that the subcomplex of Auter space of graphs of degree at most d is (d-1)-connected. We extend the definition of degree to the simplicial closure of Auter space and prove a version of Hatcher–Vogtmann’s result in this context.